The present invention relates to a mending method of a friction stir joining portion and in particularly to relates to a mending method of a friction stir joining portion of members which employ an aluminum alloy material as a base member.
A friction stir joining method is a method in which by rotating a round rod (it is called as a rotary tool) which is inserted into a joining portion of two members to be subjected to a friction stir joining, such as aluminum alloy extruded frame members, and moving the rotary tool along to a joining line of the two extruded frame members to be subjected to the friction stir joining. The friction stir joining portion of the two extruded frame members to be subjected to the friction stir joining is heated, softened and plastically fluidized.
The rotary tool is comprised of a small diameter portion which is inserted into the friction stir joining portion of the two extruded frame members and a large diameter portion which is positioned at an outside portion of the small diameter portion. A center of the small diameter portion of the rotary tool and a center of the large diameter portion of the rotary tool are positioned to the same axis.
A boundary portion between the small diameter portion and the large diameter portion of the rotary tool is inserted a little into the friction stir joining portion of the two extruded frame members. The rotary tool is inclined toward a rearward against an advancing direction of a joining of the two extruded frame members.
When the friction stir joining is carried out to the two extruded frame members, at a surface of a side of the extruded frame member to which the rotary tool is inserted, a raised portion of the extruded frame member is formed. For this reason, at the friction stir joining portion of the two extruded frame members a plate thickness of the extruded frame member becomes to be reduced.
To prevent the above stated plate thickness of the extruded frame member, at an end portion of an extruded frame member to be subjected to the friction stir joining the raised portion which projects toward a side of the rotary tool is provided, and including this raised portion the friction stir joining is carried out to the two extruded frame members.
Further, in place of the provision of the raised portion to the extruded frame member, a third plate is arranged to the two extruded frame members (a first extruded frame member and a second extruded frame member) and the friction stir joining is carried out to the two extruded frame members and the third plate.
Further, in a friction stir joining of hollow frame members, a supporting plate which is arranged orthogonal to a face plate of the hollow frame member is provided integrally and then by a force of the friction stir joining a bending of the face plate of the hollow frame member can be prevented.
The above stated technique is disclosed in Japanese application patent laid-open publication No. Hei 9-309164 (EP 0797043 A2).
FIG. 9 shows a technique for joining a side structure of a railway car 10 according to the friction stir joining. In a structure member of the side structure of the railway car 10, extruded frame members 20 and 30 (a first extruded frame member 20 and a second extruded frame member 30) are employed.
Such extruded frame members 20 and 30 are manufactured by extruding and molding, for example, aluminum alloy members (A6N01 material) are joined at a respective side edge portions and along to a joining line 40 of the first extruded frame member 20 and the second extruded frame member 30 the friction stir joining is performed on the first extruded frame member 20 and the second extruded frame member 30 and a joining bead 50 is formed between the first extruded frame extruded member 20 and the second extruded frame member 30.
As an extruded frame material of an aluminum and/or an aluminum alloy, the above stated A6N01 material is used as a railway car material, since a complicated cross-section shape large thin hollow frame member can be obtained and high anti-corrosion performance and a good welding performance can be attained.
A chemical composition of the above stated A6N01 material is 0.40-0.9% Si, less than 0.35% Fe, less than 0.35% Cu, less than 0.50% Mn, 0.40-0.8% Mg, less than 0.3% Cr, less than 0.25% Zn, less than 0.10% Ti, and Al (residual).
Next, the joining bead 50 of the first extruded frame member 20 and the second extruded frame member 30 is inspected, when there is no defect it can leave as it is and when the defect is discovered in the joining bead 50 after the mending of the defect on the joining bead 50 a hairline processing etc. is performed and accordingly a surface of the first extruded frame member 20 and the second extruded frame member 30 having a beautiful appearance feeling can be formed.
FIG. 4 shows a state in which the friction stir joining is performed along to the joining line 40 of the first extruded frame member 20 and the second extruded frame member 30 and the joining bead 50 is formed between the first extruded frame member 20 and the second extruded frame member 30.
This joining bead 50 of the first extruded frame member 20 and the second extruded frame member 30 is inspected, for example, according to a ultra supersonic defect overseeing inspection and it is assumed that a defect 60 shown in FIG. 5 has discovered on the joining bead 50.
Further, form FIG. 1 to FIG. 7 (except for FIG. 3), a line of the end portion of the raised portion is excepted. Each of a structure shown in FIG. 6 and FIG. 7 shows a conventional mending process of the defect 70 which is discovered on the joining bead 50.
Each of the first extruded frame member 20 and the second extruded frame member 30 is manufactured respectively using A6N01 material being the aluminum alloy material as a base member according to the extruding processing. The joining bead 50, which is formed by performing the friction stir joining to the first extruded frame member 20 and the second extruded frame member 30, has also a component comprised of A6N01 material same to the base member of the first extruded frame member 20 and the second extruded frame member 30.
To remove the defect of this joining bead 50, a part including this defect portion is performed with a processing using a tool such as a grinder and a mending zone 70 is formed.
Next, MIG welding (metal inert gas welding) is performed and then a mending bead 80 is formed. As MIG welding, a welding wire suited to MIG welding is used. As a material of this welding wire, a material having A5356 regulation is used.
FIG. 8 shows a state in which to the joining portion including the joining bead 50 having been mended a hairline processing 52 is performed. The hairline processing 52 has a surface having a high homogenous property against to the surfaces of the first extruded frame member 20 and the second extruded frame member 30 and leaving the surface with no painting working state such a surface can used as the side structure of the railway car 10.
When the hairline processing 52 is performed to the joining bead 50 in which the joining bead 50 according to the above stated conventional friction stir joining is mended using MIG welding, the surface of a mended portion 82 shown in FIG. 8 exhibits a different appearance against the surface of the periphery of the mended portion 82.
As to an outer appearance of the mending portion, leaving as no painting as the side structure of the railway car 10 when the joining members are used, it becomes a problem from an aspect of the outer appearance feeling.
An object of the present invention is to provide a mending method of a friction stir joining portion in which the above stated problems can be solved.
Another object of the present invention is to provide a mending method of a friction stir joining portion in which a defect of the friction stir joining portion can be removed.
A further object of the present invention is to provide a mending method of a friction stir joining portion in which a defect of a joining bead of the friction stir joining portion of two members to be subjected to a friction stir joining can be removed.
A mending method of a friction stir joining portion according to the present invention which is formed by using a friction stir joining comprises a step of forming a mending zone by removing a defect which is included in a joining bead according to a grinding processing, and a step of forming a mending bead in the formed mending zone according to TIG welding (tungsten inert gas welding) using a welding rod which is the same material to the base member.
Further, a mending method of a friction stir joining portion according to the present invention further includes a step of performing a hairline processing to a joining portion which includes the mending bead and the joining bead.